This invention relates to a magnetic-tape apparatus comprising a magnetic-head unit including a magnetic head having a head face and at least one transducing gap, which extends in the head face, for writing and/or reading information onto/from a magnetic tape. The magnetic-head unit further comprises two height limiters each having a tape-guide surface for guiding an edge of the magnetic tape, a tangent line, which is tangent to both tape-guide surfaces, extending perpendicularly to an imaginary line in the head face parallel to the transducing gap. The imaginary line and the tangent line, which are perpendicular to one another, may intersect one another or cross one another. Such a construction of the magnetic-head unit ensures that in operation the longitudinal axis of the magnetic tape extends perpendicularly to the transducing gap, so that the magnetic tape always occupies the same position relative to the transducing gap during writing and reading of information on the magnetic tape and no azimuth error can occur.
The invention further relates to a magnetic-head unit suitable for use in the magnetic-tape apparatus, which unit comprises a magnetic head having a head face and a transducing gap adjacent the head face, and two height guides, which each have a tape-guide surface.
A magnetic-tape apparatus and a magnetic-head unit of the types defined above are known from U.S. Pat. No. 4,485,420 (herewith incorporated by reference). In order to ensure that an edge of a magnetic tape remains in contact with height limiters control elements arranged opposite said height limiters press against the other edge of the magnetic tape. In the known magnetic-tape apparatus these control elements are formed by resilient means. A magnetic-head unit of the known apparatus is fixedly mounted in the magnetic-tape apparatus and is provided with a magnetic head. The magnetic head has two transducing gaps for reading and writing a left-channel and right-channel stereo/audio signal. If, in operation, the longitudinal axis of the magnetic tape is not oriented perpendicularly to the transducing gap the height limiters in conjunction with the resilient means, will correct the position of the magnetic tape at the location of the magnetic-head unit. The magnetic tape is then urged into the correct position. This gives rise to stresses in the magnetic tape, as a result of which the magnetic tape is not pressed against the head face with the same force over its entire width and may even come off the head face near one of the edges. In analog audio recording in accordance with the generally known standard Compact Cassette system this does not lead to any significant problems because the transducing gaps extend across a substantial part of the width of the magnetic tape and the signals have a large wavelength, so that during recording a small clearance between the magnetic head and the magnetic tape may exist without immediately giving rise to any appreciable signal loss.
In digital audio recording in accordance with the generally known standard Digital Compact Cassette system the magnetic head of the magnetic-tape apparatus has a comparatively large number of transducing gaps and the wavelength of the audio signals is substantially smaller than with analog audio recording. Should the magnetic tape come off the head face near one of the edges of the magnetic tape this would result in one or more transducing gaps being no longer in contact with the magnetic tape, leading to signal loss.